[Social] Postings via address@hidden bounce...

Hi all,
Perhaps not quite the right place for this, but I've been unable to get a
hold of anyone otherwise.
When I send an email from my gmail account to address@hidden
(yes, I am subscribed), I get the following back:
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Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server
for the recipient domain nongnu.org by eggs.gnu.org.
[2001:4830:134:3::10].
The error that the other server returned was:
550-Callout verification failed:
550 550 Unrouteable address
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I hope this gets seen by someone who can resolve this problem...?
Regards,
Evert